This invention relates in general to magnetic particle separators and, in particular to a magnetic particle separator in which the magnetically attractable particles are captured on a non-magnetic hollow tube inserted in a particle stream of mixed materials. The non-magnetic tube attracts magnetic particles in the stream because of magnetic rods inserted in the interior of the hollow tubes while the tubes are in the particle stream. The magnetically attractable particles are removed from the surface of the tubes by withdrawing the magnetic rods from the interior of the tubes which removes the magnetic attraction force from the tube surface. The captured particles will fall from the tube surface when the magnetic force is removed. Such devices are referred to as grate magnets since there is usually a series of tubes lying side by side in the particle stream forming a grate-like structure.
The problem with such devices is that if the magnetic rods are removed from the non-magnetic tubes while the tubes are in the particle stream, the particles captured on the tubes will be released into the stream thereby contaminating the mixture in the stream. It is therefore desirable to provide a means of interlocking the magnetic rods in the tubes such that the magnetic rods cannot be removed from the tubes while the magnetic grate is in the particle stream.
A typical application for such a device is disclosed in U.S. Pat. No. 5,071,541 METHOD AND APPARATUS FOR SORTING A MIXTURE OF PARTICLES. In this patent, a non-magnetic plastic blasting material is used to remove old paint coatings from a structure instead of using chemical stripping compounds which may be hazardous to the employees health and to the environment. During the paint removing blasting operation, small magnetically attractable particles are removed from the surface of the structure and mix with the blasting medium as it falls from the structure. In recovering the plastic blasting medium for recycling in the system, it is necessary to remove from the blasting medium as much of the foreign material as possible to insure uniform results from the system. Non-magnetically attractable particles can be removed by physical separation methods and the magnetically attractable particles removed by a separator as described in this application.